1. Field of the Invention
The present invention pertains to mountings for members loaded in tension, and in particular to the mounting of flexible drive members such as belts or chains.
2. Description of the Related Art
Many devices in use today include a tension member, either rigid or flexible, which is subjected to intermittent loads. One example of a rigid tension member is given in U.S. Pat. No. 3,306,121 which describes a screw shaft which has an end secured to an alternator mounting on an internal combustion engine, and driven by a fan belt. A coil spring disposed about the screw shaft maintains a spring tension on the fan belt. The spring is backed by a stationary mounting bracket mounted to the engine. The screw shaft is free to move through the mounting bracket to allow the spring to work against forces applied to the fan belt.
However, many systems employ flexible tensile members such as ropes and cables. U.S. Pat. No. 916,081 discloses an arrangement for applying a static tension to a flexible tension member. The tension member is passed through a mounting bracket and is connected to a hollow shaft with external threads, which also passes through the mounting bracket. On the upstream side of the bracket, a spring is held captive between the bracket and a free end of the hollow tube. A threaded nut advances the hollow tube so as to vary the spring tension applied to the tension member.
U.S. Pat. No. 1,290,964 discloses a resilient cable support in which a cable is attached to a hook, with the body of the hook being passed through a rigid support. The body of the hook is threaded to receive a threaded fastener. A spring is held captive between the threaded fastener and the mounting. By advancing the threaded fastener along the hook body, the spring tension is adjusted, which in turn adjusts the tension in the cable.
U.S. Pat. No. 2,128,030 discloses a tightener for supplying a tension to a cable. A hollow enclosure has opposed open and closed ends. A threaded attachment member extends from the closed end for securement to a stationary support. A shaft is inserted through the open end of the housing to have a first portion disposed within the housing and a second portion disposed outside of the housing. A coil spring is slid over a first portion of the shaft and is held captive thereon by an enlarged end of the shaft. The second portion of the shaft, extending outside of the housing, is connected to a cable. The coil spring acts to withdraw the second portion of the shaft into the hollow body. Initially, the second portion of the shaft is pulled outside of the hollow body to store energy in the coil spring, and a pin is inserted in the second portion of the shaft to prevent retraction into the hollow body. After the device is installed between a rigid support and a cable, the pin is removed to allow a slight expansion of the spring and a resulting tensioning of the cable. In order to assemble the device, the hollow body must be made of several components, herein three components, a part resembling a pipe nipple, and a pair of threaded end caps to be fitted to the pipe nipple, one having a central opening through which the second portion of the shaft is inserted, prior to assembly. The device is generally unsuitable for use with tension members having a threaded shaft at the end to be secured, and the device is costly to fabricate.
U.S. Pat. No. 3,109,213 discloses an automatic tension release device for cords which contract when wet. A cord is passed through a cylindrical barrel having an arrangement resembling a ball bearing race at one end. The bearing balls engage the cord, preventing movement relative to the cylinder. The cylinder is inserted in a conical housing which presses the bearing balls against the cord. The conical tube is secured with a bail to a stationary support. A second cord extends between the cylinder and the stationary support. The second cord is of a design to shrink faster than the cord whose tension is being controlled. When the second cord is wetted, it contracts to move the cylinder relative to the conical tube, thus allowing the bearing balls to move away from the cord being controlled, thus releasing tension on the cord.
U.S. Pat. No. 3,343,858 describes a resilient link in which a generally cylindrical housing has a closed end for attachment to a tension member, and an opposing open end having a central bore and a radially directed slot extending from the central bore. The housing has a side portion removed, forming an opening which extends to the slot and the central bore, thus forming a continuous passageway. A shaft having a first, enlarged end and a second free end is inserted through the passageway of the housing with the shaft aligned with the central bore of the housing. A coil spring and a disk-like wall are slid over the second end of the shaft with the disk-like wall compressing the spring against the enlarged, first end of the shaft. A removable pin holds the disk-like wall in position, storing energy in the coil spring. The shaft assembly is then inserted in the passageway of the housing, with the spring, disk-like wall and enlarged end of the shaft received in the body of the housing, and the second, free end of the shaft extending through the bore at the open end of the housing. The removable pin is accessible through the open side of the housing, so as to be removable once the resilient link is installed in a system. No other adjustment is provided in the resilient link, except for the provision of allowing the spring to expand once the pin is removed. The device is of a complicated construction and expensive to fabricate.
A need has existed for an improved snubber device for tensile members, particularly flexible tensile members. For example, improved mounting devices have been sought for garage door openers having a drive chain or drive belt coupled to a trolley providing attachment to a garage door. Heretofore, certain garage door opener types have had drive members provided with free ends, which are mounted to spaced portions of the trolley. One free end of the drive member is provided with a threaded shaft, which is inserted through a mounting wall on the trolley. By manipulating nut fasteners mated to the threaded shaft, the threaded shaft can be moved relative to the trolley mounting wall, thereby adjusting the tension on the drive member. Snubber devices have been sought for use with the above-mentioned types of garage door openers and similar mounting systems for tension members. However, in many applications, such snubber devices must be both economical to fabricate and quickly installed without difficulty, so as to be commercially attractive in competitive markets.